The present invention relates to an apparatus for forming a plastic bag and for sealing the open end of a plastic bag. The plastic bags formed and sealed by the apparatus of the invention are primarily intended for the storage and preservation of food stuffs. But, of course, they may be used for holding any objects.
Apparatus for sealing the open end of a plastic bag are known. U.S. Pat. No. 3,847,712 shows a sealing apparatus having an oblong, rectangular cross-section heat conductive member which is heated. The heat conductive member has a knife edge formed on one side thereof and extending along its length. The heat conductive member is rotatable around its longitudinal axis so that either the knife carrying surface or another surface may be selected to contact a plastic bag laid over the conductive member. With the knife edge contacting the bag, in the case of an ordinary plastic bag comprised of a single layer of plastic, melt trimming or sealing of the bag is performed by the knife edge. With the heat conductive member rotated so that another edge thereof contacts the plastic bag, the open end of the bag may be sealed with a heat seal band, as occurs with so-called boiler bags that are comprised of two layers of plastic.
Known heat seal apparatus are usually used with completed plastic bags of previously determined size. The size of the bag may be considerably greater than the capacity required to hold the amount of material intended to be inserted therein. This is uneconomical and in connection with boilable bags, is quite high in cost. One way in which this problem is handled is to sell bags of various sizes. But there is no limit to the kinds and sizes of food or other storable objects that are bagged in a typical household. As a result, even with a full selection of bag sizes, it is not unusual to have a bag considerably larger than the item to be held.
Furthermore, conventional bag forming apparatus do not include means for cutting off part of a boilable bag or the like. It has thus become necessary to employ a separate scissors for forming a cut at the end of a bag for the purpose of initiating removal part or the end of the bag.
It is space consuming to store the bags of various sizes now offered for sale. Furthermore, it is difficult to maintain an accurate count of the total number of bags of every size remaining available, whereby it is quite difficult for the consumer to determine when he must order an additional supply of a particular size bag.